XML and ASP

You're comparing apples to oranges. XML is meant to move data between apps/systems (temporarily holding data), it was never meant to replace a full fledged Relational Database System. XML can hold data permanently and become a database in itself but that is not where it's strength lies. If you're currently using a text file for storing your data then you should definitely upgrade to XML, if you're using Access then maybe you should consider upgrading to SQL Server.

I use XML to temporarily store data to pass to different areas of my apps, but it is partnered with a SQL Server backend.

As Peter said the strength behind the xml framework is its ability to share data between different systems, apps and platforms. We just finished an app that transferred our corporate-base database info to our salesman on the road via XML. So in my experience xml has been utilised as an interim step of data transfer etc

There are XML databases on the market these days that sound great, I haven't looked in to the details of them yet, but I would still never go past a full on power database like SQL server or MySQL.

at least not yet...

Ok so I am not exactly comparing apples to oranges but I might look for alternate ways of storing my information and then use xml to transfer it between systems. Now you meantioned mysql and sql. Could I find a cheap place to give me ONLY access to sql database space and if so, could I use that sql space from my other domain?

While it is possible you should avoid using a remote SQL Server, performance will suffer. You should try to have the webserver and the database server on the same network, or as close as possible.

I'm not sure of any hosts that just offer db hosting, but you can probably find many that offer mysql and php for around 30-50 per year, and sql and asp for a little more.